Zinc oil additives
Of course this is written by Rislone that produces a additive. I'm putting some in my Valvoline Conventional. If some of you believe it has to be mixed with the oil in the bottle that's your choice. If you want to pay $9-10 a quart for some hot rod oil that's your choice.
The Effects of Zinc Oil Additives on Older Engines | Rislone.